Systems and methods for metastable activated radical selective strip and etch using dual plenum showerhead

ABSTRACT

A substrate processing system for selectively etching a substrate includes a first chamber and a second chamber. A first gas delivery system supplies an inert gas species to the first chamber. A plasma generating system generates plasma including ions and metastable species in the first chamber. A gas distribution device removes the ions from the plasma, blocks ultraviolet (UV) light generated by the plasma and delivers the metastable species to the second chamber. A substrate support is arranged below the gas distribution device to support the substrate. A second gas delivery system delivers a reactive gas species to one of the gas distribution device or a volume located below the gas distribution device. The metastable species transfer energy to the reactive gas species to selectively etch one exposed material of the substrate more than at least one other exposed material of the substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/436,708, filed on Dec. 20, 2016, U.S. Provisional Application No.62/513,615, filed on Jun. 1, 2017, and U.S. Provisional Application No.62/569,094 filed on Oct. 6, 2017. The entire disclosures of theapplications referenced above are incorporated herein by reference.

FIELD

The present disclosure relates to substrate processing systems, and moreparticularly to substrate processing systems for stripping photoresistor selectively removing film from a substrate with high selectivity.

BACKGROUND

The background description provided here is for the purpose of generallypresenting the context of the disclosure. Work of the presently namedinventors, to the extent it is described in this background section, aswell as aspects of the description that may not otherwise qualify asprior art at the time of filing, are neither expressly nor impliedlyadmitted as prior art against the present disclosure.

Substrate processing systems may be used to strip photoresist on asubstrate such as a semiconductor wafer. The substrate processingsystems typically include a processing chamber, a gas distributiondevice and a substrate support. During processing, the substrate isarranged on the substrate support. Different gas mixtures may beintroduced into the processing chamber and radio frequency (RF) plasmamay be used to activate chemical reactions.

Plasma-based strip technologies typically use radical species to removea photoresist layer. Substrate processing systems may use capacitivelycoupled plasma (CCP) or inductively coupled plasma (ICP) to generateradicals directly above the substrate. CCP and ICP processes aretypically used for in-situ photoresist strip after performing a plasmaetch process. Advantages of these processes include stripping without avacuum break and a relatively high removal rate. However, ions or vacuumultraviolet (VUV) photons generated by the direct plasma may damageunderlying layers and cause measurable substrate loss in areas exposedto the direct plasma.

Substrate processing systems using downstream plasma sources such asICP, electron cyclotron resonance (ECR) or microwave sources may also beused. The amount of exposure of the substrate to ion and photon flux canbe minimized using a showerhead. While this approach has lower substrateloss, the removal rate is typically lower due to loss through surfacerecombination on dome/tube surfaces, chamber walls and/or showerheadsurfaces. Furthermore, there is still measurable substrate loss due tothe generated active oxidation species from background species such asmolecular oxygen (O₂), water (H₂O), atomic O, OH and sputtering fromdome/tube materials that are directly exposed during the plasmageneration.

SUMMARY

A substrate processing system for selectively etching a substrateincludes a first chamber and a second chamber. A first gas deliverysystem supplies an inert gas species to the first chamber. A plasmagenerating system generates plasma including ions and metastable speciesin the first chamber. A gas distribution device is arranged between thefirst chamber and the second chamber to remove the ions from the plasma,to block ultraviolet (UV) light generated by the plasma and to deliverthe metastable species to the second chamber. A substrate support isarranged below the gas distribution device to support the substrate. Asecond gas delivery system delivers a reactive gas species to one of thegas distribution device or a volume located below the gas distributiondevice. The metastable species transfer energy to the reactive gasspecies to selectively etch one exposed material of the substrate morethan at least one other exposed material of the substrate.

In other features, the one exposed material of the substrate includesphotoresist. The substrate processing system etches the photoresist at aratio greater than 50:1 relative to at least one other exposed materialof the substrate. The at least one other exposed material is selectedfrom a group consisting of silicon, silicon germanium, and silicondioxide. The inert gas species is selected from a group consisting ofhelium, argon, neon, krypton and xenon.

In other features, the reactive gas species is selected from a groupconsisting of molecular oxygen, molecular nitrogen, molecular hydrogen,nitrogen trifluoride and carbon tetrafluoride. The plasma generatingsystem includes an inductive coil arranged around an outer surface ofthe first chamber and wherein the plasma generating system selectivelysupplies 500 W to 5 kW to the coil to generate the plasma.

In other features, the substrate support controls a temperature of thesubstrate to a predetermined temperature range from 75° C. to 225° C.during etching. The inert gas species and the reactive gas species aresupplied at a flow rate of 50 sccm to 10 slm. A light blocking structureis arranged above the gas distribution device.

In other features, the light blocking structure comprises a first lightblocking plate including a first plurality of through holes. A secondlight blocking plate is located between and spaced from the first lightblocking plate and the gas distribution device and includes a secondplurality of through holes. The first plurality of through holes is notaligned with the second plurality of through holes. The metastablespecies flow through the first plurality of through holes and the secondplurality of through holes to the gas distribution device.

In other features, the first plurality of through holes and the secondplurality of through holes have a diameter in a range from 0.1″ to 2″.The first light blocking plate and the second light blocking plate havea thickness in a range from 0.1″ to 0.5″. Each of the first plurality ofthrough holes and the second plurality of through holes comprises 10 to3000 holes.

In other features, an annular plate is located above the first lightblocking plate, includes a radially outer edge that extends to asidewall of the first chamber and includes a radially inner edge havinga diameter that is less than an outer diameter of the first lightblocking plate.

In other features, the light blocking structure comprises a first lightblocking plate without through holes and including a radially outer edgethat is spaced from a sidewall of the first chamber. A second lightblocking plate is located between and spaced from the first lightblocking plate and the gas distribution device and includes a pluralityof through holes. The metastable species flow around the first lightblocking plate and through the plurality of through holes of the secondlight blocking plate to the gas distribution device.

In other features, the light blocking structure comprises a lightblocking plate without through holes. The light blocking plate includesa radially outer edge that is spaced from a sidewall of the firstchamber. An annular plate is spaced from the light blocking plate andthe gas distribution device, extends to the sidewall of the firstchamber and has an inner diameter that is less than an outer diameter ofthe light blocking plate. The metastable species flow around the lightblocking plate and through the inner diameter of the annular plate tothe gas distribution device.

In other features, the gas distribution device includes a first surfacefacing the first chamber and a second surface facing the second chamber.A gas inlet receives the reactive gas species from the second gasdelivery system. Channels located in the gas distribution device deliverthe reactive gas species from the gas inlet to a plurality of locationsabove the substrate. A first plurality of through holes extends from thechannels through the second surface to the second chamber. A secondplurality of through holes extends from the first surface to the secondsurface to deliver the metastable species to the second chamber.

In other features, the channels include an annular channel arrangedadjacent to a radially outer edge of the gas distribution device and aplurality of connecting channels extending across the gas distributiondevice between the annular channel.

In other features, the gas distribution device includes a first surfacefacing the first chamber and a second surface facing the second chamber.A plurality of through holes define an indirect path through the gasdistribution device from the first surface to the second surface.

In other features, the gas distribution device includes a first surfacefacing the first chamber and a second surface facing the second chamber.A first gas inlet receives a first reactive gas species from the secondgas delivery system. A second gas inlet receives a second reactive gasspecies from the second gas delivery system. First channels are locatedin the gas distribution device to deliver the first reactive gas speciesfrom the first gas inlet to a plurality of locations in a first zoneabove the substrate. Second channels are located in the gas distributiondevice to deliver the second reactive gas species from the second gasinlet to a plurality of locations in a second zone above the substrate.A first plurality of through holes extends from the first channelsthrough the second surface to deliver the first reactive gas species tothe second chamber. A second plurality of through holes extends from thesecond channels through the second surface to deliver the secondreactive gas species to the second chamber. A third plurality of throughholes extends from the first surface to the second surface to deliverthe metastable species to the second chamber.

In other features, a portion of the first channels extends radiallyinwardly to the first zone. A portion of the second channels extendsradially inwardly to the second zone. The first plurality of throughholes, the second plurality of through holes, and the third plurality ofthrough holes are arranged in concentric circles. A light blockingstructure is arranged above the gas distribution device.

In other features, the light blocking structure comprises a plateincluding arcuate holes that are misaligned relative to the firstplurality of through holes, the second plurality of through holes, andthe third plurality of through holes.

In other features, the plasma generating system further comprises apulse modulator configured to vary a pulsing parameter of an RF signalthat generates plasma during etching. The pulse modulator varies atleast one of a duty cycle and an amplitude of the RF signal suppliedduring etching. The pulse modulator varies the pulsing parameter betweena first state having a first RF power and second state having a secondRF power that is less than the first RF power.

In other features, the pulse modulator switches between the first stateand the second state at predetermined intervals during etching. Thepulse modulator receives an optical feedback signal and switches betweenthe first state and the second state during etching based on the opticalfeedback signal. A first intensity of the metastable species during thefirst state is less than a second intensity of the metastable speciesduring the second state. The RF signal has an envelope selected from agroup consisting of a square wave, a rectangular wave, a sinusoidalwave, and a saw tooth wave.

In other features, the RF signal has a rectangular wave envelope andswitches at a duty cycle that is less than 100% between a firstamplitude and a second amplitude. The first amplitude is greater thanthe second amplitude and wherein the second amplitude is greater than orequal to zero.

Further areas of applicability of the present disclosure will becomeapparent from the detailed description, the claims and the drawings. Thedetailed description and specific examples are intended for purposes ofillustration only and are not intended to limit the scope of thedisclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will become more fully understood from thedetailed description and the accompanying drawings, wherein:

FIG. 1 is a functional block diagram of an example of a substrateprocessing system according to the present disclosure;

FIG. 2 is a side cross-sectional view of an example of a substrateincluding a silicon layer and a photoresist layer to be stripped;

FIG. 3 is a graph illustrating optical emission spectroscopy (OES)characterization of the plasma with He only;

FIG. 4 is a graph illustrating OES characterization of He plasma with O₂injection from the side between the showerhead and the substratesupport;

FIG. 5 is a flowchart illustrating an example of a method forselectively stripping photoresist according to the present disclosure;

FIG. 6 is a plan view illustrating an example of a gas distributiondevice including a dual gas plenum according to the present disclosure;

FIG. 7 is a first cross-sectional view of the dual gas plenum of FIG. 6according to the present disclosure;

FIG. 8 is a second cross-sectional view of the dual gas plenum of FIG. 6according to the present disclosure;

FIG. 9 is a plan view illustrating an example of a light blockingstructure for the gas distribution device according to the presentdisclosure;

FIG. 10 is a side cross-sectional view of an example of a light blockingstructure and the dual gas plenum according to the present disclosure;

FIGS. 11-13 are side cross-sectional views of other examples of lightblocking structures and the dual gas plenum according to the presentdisclosure;

FIG. 14 is a side cross-sectional view of a gas distribution deviceincluding a showerhead and a dual gas plenum;

FIGS. 15A and 15B is a side cross-sectional view of another example of adual gas plenum according to the present disclosure;

FIG. 16 is a plan view of another example of a zoned dual gas plenumaccording to the present disclosure;

FIGS. 17 and 18 are graphs illustrating examples of net loss ofamorphous silicon (a-Si) for different process temperatures and periodsaccording to the present disclosure;

FIG. 19 is a perspective view of a gas distribution device including azoned dual gas plenum according to the present disclosure;

FIG. 20 is a perspective view of a blocking plate of FIG. 19 ;

FIG. 21 is a partial cross-sectional view of a bottom surface of thedual gas plenum of FIG. 19 ;

FIG. 22 is a functional block diagram of another example of a substrateprocessing system including plasma pulsing that is selected orcontrolled based on optical feedback according to the presentdisclosure;

FIG. 23A is a graph illustrating enhanced long lifetime species createdby pulsing the plasma according to the present disclosure;

FIG. 23B is a graph illustrating a fast electron effect created bypulsing the plasma according to the present disclosure;

FIG. 24A is a graph illustrating an example of a pulsed signal tomodulate RF plasma signal according to the present disclosure;

FIG. 24B is a graph illustrating an example of the pulsed signalmodulating the RF plasma signal according to the present disclosure;

FIG. 24C is a graph illustrating an example of a pulsed level-to-levelsignal modulating the RF plasma signal according to the presentdisclosure;

FIGS. 25A to 25D illustrate other examples of pulsed signals formodulating the RF plasma signal according to the present disclosure;

FIG. 26 is a flowchart illustrating a method for identifying pairs of RFpulsing parameters having a desired intensity ratio according to thepresent disclosure;

FIG. 27 is a flowchart illustrating a method for using feedback from anoptical emission spectroscopy (OES) sensor to switch a pulsed signalbetween different pulsing states to modulate the RF plasma signalaccording to the present disclosure;

FIG. 28 is a flowchart illustrating a method for pulsing a pulsed signalbetween different pulsing states at fixed intervals according to thepresent disclosure;

FIG. 29A is a bottom perspective view illustrating a spacer that islocated centrally for supporting a blocking plate; and

FIG. 29B is a side view illustrating the blocking plate with the spacerthat is located centrally in a gas distribution device.

In the drawings, reference numbers may be reused to identify similarand/or identical elements.

DETAILED DESCRIPTION

Systems and methods according to the present disclosure utilize a plasmasource to supply plasma including metastable species and ions in anupper chamber (e.g., element 60 shown in FIGS. 1 and 22 ). Themetastable species diffuse through a first showerhead located betweenthe upper chamber and a substrate support arranged in a lower chamber(e.g., element 62 shown in FIGS. 1 and 22 ).

The first showerhead blocks trace amounts of He ions and vacuumultraviolet (VUV) or UV emission. In some examples, a second showerheadmay be arranged between the first showerhead and the substrate support.The second showerhead may be used to re-direct active strip species oretch species uniformly above the substrate.

Active etching species are injected from a side of the processingchamber between the first showerhead (or the second showerhead) and thesubstrate support. The metastable species transfer energy to the activeetching species to generate radicals for film removal.

For example, an ICP source and an inert plasma gas such as Helium (He)may be used to generate He active species including low kinetic energy(<1 eV) metastable species (He*) that have high excitation energy in therange of 19-21 eV. The metastable species have a lifetime in a range of10 seconds or greater. The metastable species diffuse through the firstshowerhead and are used to activate the etching species. The reactivegas or gas mixture is injected from a different location than the activeplasma source to reduce erosion of chamber surface materials.

Referring now to FIG. 1 , an example substrate processing system 50 forselectively stripping film such as photoresist or other film is shown.As used herein, selective stripping refers to stripping exposed filmmade of a first material at a higher rate than stripping of one or moreother exposed films made of other materials. In some examples, the ratioof stripping of the target film relative to the other (non-target) filmsis greater than or equal to 50:1, 200:1, 500:1, 2000:1, etc. While theforegoing example will be described in the context of a substrateprocessing system using inductively coupled plasma (ICP), the presentdisclosure may be applied to other substrate processing systemsgenerating plasma using other plasma sources.

The substrate processing system 50 includes a plasma source 51 and asubstrate support 52 such as an electrostatic chuck, pedestal or othertype of substrate support. In some examples, the plasma source 51includes an ICP source. As can be appreciated, the plasma source 51 mayinclude other suitable plasma sources such as CCP, ECR or microwaveplasma sources.

A substrate 54 is arranged on the substrate support 52 during theselective stripping. In some examples, the substrate support 52 istemperature controlled (heating and/or cooling) using one or moretemperature control elements (TCEs) 55, as resistive heaters 56, coolantchannels 58, or other types of thermal control devices. The substratesupport 52 may include a single temperature control zone or a pluralityof temperature control zones that are individually controlled.

The substrate processing system 50 includes an upper chamber 60. In someexamples, the upper chamber 60 has a dome shape, although other shapescan be used. When ICP plasma is used, a coil 64 is arranged around anouter surface of the upper chamber 60. A gas injector 68 injects plasmagas into the upper chamber 60. In some examples, the gas injector 68injects the plasma gas in one or more directions (such as center andside gas injection directions as shown in FIG. 1 ).

The substrate processing system 50 further includes a gas distributiondevice 70 such as a platen including a plurality of spaced through holes76. The gas distribution device 70 is used to filter ions generated bythe plasma and to block VUV or UV radiation. The gas distribution device70 is arranged between the substrate support 52 and the upper chamber60. Secondary gas injectors 82 inject secondary gas in a locationbetween the gas distribution device 70 and the substrate support 52. Insome examples, the secondary gas injectors 82 are arranged at uniformintervals around the periphery of the processing chamber. In someexamples, another gas distribution device 84 (such as a platen includinga plurality of spaced through holes 86) may be arranged between the gasdistribution device 70 and the substrate support 52. The gasdistribution device 84 may be used to redirect active strip species oretch species above the substrate.

If ICP plasma is used, an RF generating system 87 generates and outputsan RF power to the coil 64. For example only, the RF generating system87 may include an RF generator 88 that generates RF power that is fed bya matching network 89 to the coil 64.

A gas delivery system 90-1 includes one or more gas sources 92-1, 92-2,. . . , and 92-N (collectively gas sources 92), where N is an integergreater than zero. The gas sources 92 are connected by valves 94-1,94-2, . . . , and 94-N (collectively valves 94) and mass flowcontrollers 96-1, 96-2, . . . , and 96-N (collectively mass flowcontrollers 96) to a manifold 98. Another gas delivery system 90-2 maybe used to deliver the secondary gas to the secondary gas injectors 82.As can be appreciated, the gas delivery systems 90 may be simplified inthe case that the substrate processing system uses a single plasma gasand a single secondary gas.

A temperature controller 106 may be connected to the TCEs 55 such as theresistive heaters 56. The temperature controller 63 may communicate withone or more temperature sensors (not shown) that sense a temperature ofthe substrate support or the substrate and to a coolant controller 108to control coolant flow through the coolant channels 58. For example,the coolant controller 108 may include a coolant pump, a reservoirand/or one or more temperature sensors (not shown). A valve 130 and pump132 may be used to control pressure in the processing chamber and toevacuate reactants therefrom. A system controller 140 may be used tocontrol components of the substrate processing system 10 as shown inFIG. 1 .

Systems and methods according to the present disclosure generate plasmautilizing inert gas to generate a high density of metastable species.The metastable species carry high enough chemical energy to excite otheractive radical species introduced downstream. The systems and methodsdescribed herein spatially decouple plasma generation and etchingspecies production. Advantages include reduced charged ions and VUVand/or UV light emission as compared to direct plasma such as ICP andcapacitively coupled plasma (CCP). The systems and methods describedherein have higher radical density above the substrate as compared todownstream plasma with much lower recombination loss. The proposedsystems and methods have separate plasma generation and active speciesgeneration, which reduces erosion of chamber materials exposed to thehigh density direct plasma. The systems and methods described hereinhave higher strip rates, higher etch selectivity and lower substrateoxidation or loss.

In some examples, the process is operated using an ICP chamber with ICPpower in a range from 500 W to 5 kW. In some examples, the RF powerapplied to the inductive coil is at 13.56 MHz, although otherfrequencies can be used. In some examples, the process is performed at achamber pressure range of 10 mTorr to 10 Torr. In some examples, theplasma gas or gas mixture is supplied at a flow rate in a range from 50standard cubic centimeters per minute (sccm) to 10 standard liters perminute (slm). In some examples, reactive gas is supplied at a flow ratein a range from 50 sccm to 10 slm.

In some examples, the plasma gas or plasma gas mixture includes an inertgas such as He, argon (Ar), neon (Ne), krypton (Kr), xenon (Xe), andmixtures thereof. In some examples, the active etching gas includes atleast one of molecular oxygen (O₂), molecular nitrogen (N₂), molecularhydrogen (H₂), carbon tetrafluoride (CF₄), nitrogen trifluoride (NF₃),and/or their mixtures.

In use, the plasma source creates plasma including metastable speciesand ions in the upper chamber. The metastable species diffuse throughthe showerhead(s). Active etching species are injected from the side ofthe chamber under or between the showerhead(s). The metastable speciestransfer energy to the active etching species to generate radicals forphotoresist removal.

Referring now to FIG. 2 , a substrate 150 includes one or moreunderlying layers 154. A silicon dioxide layer 158 is arranged on theunderlying layers 154. A photoresist layer 160 is arranged on someportions of the silicon dioxide layer 158. After processing such asetching is performed (at 162) to etch the silicon dioxide layer 158, thephotoresist layer 160 needs to be removed. The process for stripping thephotoresist layer 160 is preferably performed without loss or damage tothe silicon dioxide layer 158.

The plasma source generates plasma by igniting a plasma gas. Metastableatoms that are produced (e.g. He*) exit the plasma source through theshowerhead(s). The showerhead(s) filter most if not all energeticdamage-producing ions and vacuum ultraviolet light (VUV) and/or UVlight. The metastable atoms are then mixed with a secondary gas (such asO₂) injected under or between the showerhead(s) and the substratesupport. For example, the secondary gas can be injected from the sideinjector ports. The injected gas species can be excited by He*metastable through penning ionization: He* (2³S)+O₂→O₂ ⁺+He+e− andfurther dissociated to atomic O* species. It is beneficial for certainprocess to generate molecular radical species to increase strip or etchselectivity. While mixing O2 within He plasma, most of the species areatomic oxygen. The excited molecular O2 impinge on thephotoresist-coated substrate can remove the film, but formsself-limiting layer on Silicon, silicon germanium or other substratesthat need to be protected.

Referring now to FIGS. 3 and 4 , optical emission spectroscopy (OES)characterization of He only plasma and He plasma with secondary O₂ gasinjection is shown. In FIG. 3 , OES characterization of the plasma withHe only is shown. In FIG. 4 , OES characterization of He plasma with O₂injection from the side under the showerhead is shown. The net effect isthat photoresist is stripped by the O* atoms with very low damage to Si(e.g. very small loss of SiO₂) and also very high strip rate.

The injection of O₂ gas from the side quenched most of the lightemission from He active species as shown in FIG. 4 . The opticalemission spectra shows dominant O₂ emissions at 777 nm and 844 nm, whichcorrespond to characteristic optical emission lines of activated oxygenspecies.

In the following comparison, an O₂/N₂ downstream plasma process has beenoptimized to remove a surface modification layer with minimum amorphoussilicon (a-Si) substrate loss. 5× higher organic layer removal amountcan be demonstrated with comparable a-Si substrate loss. The followingexample used increased pressure for O₂/N₂ process to minimize theenergetic O₂ or O⁻ species, while the process described (He/O₂) can berun at 4× lower pressure to increase the efficiency of activated radicalspecies.

Si loss (A) Baked PR Baked PR Pressure (minus Removal (A) Removal (A)Process (torr) metrology) 20 s 200 s O2/N2 4 3.3 12 368 He Only 1.1 6.56 129 He Activated O2 1.1 3.8 133 1745 He Activated O2 2.0 1.2-1.4 242500

Referring now to FIG. 5 , a method 184 for stripping photoresistaccording to the present disclosure is shown. At 186, a substrate isarranged in a processing chamber. At 188, plasma is supplied to theprocessing chamber by a plasma source. At 190, ions and VUV or UV lightis at least partially filtered by one or more showerheads arrangedbetween the plasma source and the substrate support. At 192, thesecondary gas is supplied between at least one of the showerheads andthe substrate support. When the strip period is over as determined at194, the plasma source and secondary gas are turned off at 196.

While the foregoing disclosure relates to photoresist strip, the systemsand methods described herein can be used for other purposes. In otherexamples, a gas such as molecular nitrogen N₂ can be excited by themetastable species and used downstream to nitride a film or to treat asurface. For example, a titanium film can be exposed to nitride (e.g. Tiand N₂→TiN). In another example, a tungsten film can be treated (e.g.treatment of W with N* would produce WN that would is more difficult toremove with fluorine than is W).

Referring now to FIG. 6 , a gas distribution device 200 includes a dualgas plenum 202 for delivering reactant gas species and excited gasspecies including metastable species according to the present disclosureis shown. The dual gas plenum 202 delivers a mixture of the reactant gasspecies and excited gas species to the lower chamber without mixing inthe upper chamber.

In some examples, a flow ratio of excited gas species to reactant gasspecies is in a range from 1.3 to 10:1, although other ratios may beused. In some examples, the process period is in a range from 30 s to270 s, although other periods may be used. In other examples, theprocess period is in a range from 60 s to 240 s, although other periodsmay be used. In some examples, the process temperature is in a rangefrom 75° C. to 225° C., although other process temperatures may be used.In other examples, the process temperature is in a range from 100° C. to200° C., although other process temperatures may be used. In someexamples, loss of amorphous silicon or silicon germanium (SiGe) isreduced by over 50% as compared to prior strip processes.

The gas distribution device 200 includes an upper flange 204, sidewalls206 and a bottom surface 208 (forming an upper surface of the dual gasplenum 202). The dual gas plenum 202 includes a gas inlet 210 forreceiving a reactant gas species such as molecular oxygen (O₂),molecular nitrogen (N₂), molecular hydrogen (H₂), nitrogen trifluoride(NF₃), methane (CH₄), and combinations thereof. The reactant gas speciesis shown by arrows with dotted lines in FIGS. 6-16 .

The dual gas plenum 202 defines an annular channel 220 and connectingchannels 224. The connecting channels 224 extend between opposite sidesof the annular channel 220 across inner portions of the bottom surface208. The annular channel 220 may be formed at a location between thesidewalls 206 and the bottom surface 208. The annular channel 220 andthe connecting channels 224 are in fluid communication with the gasinlet 210. The reactant gas mixture flows through the annular channel220 and into the connecting channels 224. Downwardly directed thoughholes shown in FIG. 7 direct the reactant gas mixture from theconnecting channels 224 into the lower chamber towards the substrate aswill be described further below.

Areas 228 located between the connecting channels 224 include aplurality of through holes 230 that pass through the bottom surface 208.As can be appreciated, only some of the plurality of through holes 230are shown for purposes of illustration and clarity. In some examples,the plurality of through holes 230 have a circular cross section anduniform spacing, although other cross sections and/or non-uniformspacing can be used. In some examples, the plurality of through holes232 have a diameter in a range from 3 mm to 10 mm, although otherdiameters may be used.

Plasma is generated in the upper chamber using a plasma gas mixtureincluding one or more gases selected from a group consisting of helium(He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), molecularnitrogen (N₂), and combinations thereof. Excited gas species generatedby the plasma are shown by arrows with solid lines in FIGS. 6-16 .

Referring now to FIGS. 7-8 , cross-sectional views of the bottom surface208 of the dual gas plenum 202 are shown. In FIG. 7 , a firstcross-sectional view taken along the connecting channels 224 is shown.Reactant gas is supplied to the annular channel 220, which suppliesreactant gas to the connecting channels 224. A plurality of throughholes 232 fluidly connects the connecting channels 224 to the lowerchamber. In some examples, the plurality of through holes 232 have adiameter in a range from 0.1 mm to 1 mm, although other diameters may beused. The plurality of through holes 232 can be located along theconnecting channels 224 with uniform or non-uniform spacing.

In FIG. 8 , a second cross-sectional view taken through the area 228 isshown. The plurality of through holes 230 pass through the bottomsurface 208 from the upper chamber to the lower chamber. As can be seen,the flow paths of the excited gas species and the reactant gas speciesare separate until they reach the lower chamber.

Referring now to FIG. 9 , a light blocking structure 240 may be arrangedbetween the plasma and the dual gas plenum 202. The light blockingstructure 240 may be used to block vacuum ultraviolet (VUV) lightgenerated by the plasma. In other words, the light blocking structure240 prevents a line of sight path between the plasma in the upperchamber and the substrate in the lower chamber.

In some examples, the light blocking structure 240 includes (from top tobottom) an annular plate 250 including a radially outer surface adjacentto and/or abutting the sidewall 206, a first blocking plate 260including through holes 264 (shown in solid lines) and a second blockingplate 270 including through holes 274 (shown in dotted lines). In someexamples, the plurality of through holes 264 are located in an offsetlocation relative to the plurality of through holes 274. In someexamples, the plurality of through holes 264 and 274 have a circularcross-section, although other cross-sections can be used. While theplurality of through holes 264 and 274 are shown as having roughly thesame diameter, different size through holes can be used (for example asshown at a center region of the first blocking plate 260). In someexamples, hole diameter is in a range from 0.1″ to 2″, the number ofholes is in a range from 10 to 3000 holes, a thickness of the plate isin a range from 0.1″ to 0.5″

The light blocking structure 240 may include various arrangements of theblocking plates (with or without through holes) and/or annular platesarranged above the dual gas plenum 202. For example in FIG. 10 , theannular plate 250 is arranged above the first blocking plate 260, whichis arranged above the second blocking plate 270. In some examples, theannular plate 250 is attached adjacent to or abuts the sidewall 206. Theannular plate 250 can be attached to a rest on the sidewall 206 usingfasteners, notches (in the side wall or the annular plate) andprojections (in the annular plate or the side wall), or other fasteningdevices (not shown).

In some examples, a radially inner edge of the annular plate 250 isradially spaced in a range from 0.5″ to 3″ from the radially outer edgeof the annular plate 250. In other examples, the light blockingstructure 240 rests on the bottom surface 208 and is not directlyattached to the sidewalls 206. In some examples, the first blockingplate 260 is attached to a lower surface of the annular plate 250 by twoor more spacers 282. In some examples, the spacers 282 may be attachedto the annular plate 250 and the first blocking plate 260 by fasteners(not shown) such as screws, threads, rivets, adhesive, welding, etc.

In use, excited gas species generated by the plasma in the upper chamberflow through the light blocking structure 240 such that no direct lineof sight exists between the plasma and the substrate. The excited gasspecies flow through the light blocking structure 240 and the pluralityof through holes 230 into the lower chamber as shown in FIG. 8 while thereactant gas species flows through the annular channel 220, theconnecting channels 224, and the plurality of through holes 232 beforeflowing into the lower chamber as shown in FIG. 7 . In some examples, aradially inner edge of the annular plate 250 is arranged inwardly of aradially outer edge of one or more of the first and second blockingplates 260, 270, respectively.

Referring now to FIG. 11-13 , other variations of the light blockingstructure 240 are shown. In FIG. 11 , the light blocking structure 240includes (from top to bottom) a first blocking plate 290 without throughholes, a second blocking plate 300 including a plurality of though holes304, and the annular plate 250. The first blocking plate 290 may have adiameter that is slightly less than a diameter defined by the sidewalls206. A gap 308 is created between a radially outer edge of the firstblocking plate 290 and the sidewalls 206. In some examples, the gap isless than or equal to 0.5″. In some examples, the gap is less than orequal to 0.1″. Spacers 282 may be used to provide a gap between thesecond blocking plate 300 and the first blocking plate 290.

Excited gas species flow through the gap 308 and are directed by theannular plate 250 and the second blocking plate 300 to the plurality ofthrough holes 304. The excited gas species flow through the plurality ofthrough holes 230 of the gas distribution device 200 and into the lowerchamber as shown in FIG. 8 . Likewise, the reactant gas species flowthrough the annular channel 220, the connecting channels 224 and theplurality of through holes 232 into the lower chamber as shown in FIG. 7.

In FIG. 12 , the light blocking structure 240 includes (from top tobottom) a first blocking plate 310 including through holes 314, a secondblocking plate 320 including through holes 324, and the annular plate250. The first blocking plate 310 may also define the gap 308. Thesecond blocking plate 320 includes a radially outer portion that restson a radially inner portion of the annular plate 250. Spacers 282 may beused between the second blocking plate 320 and the first blocking plate310.

The first blocking plate 310 may have a diameter that is slightly lessthan a diameter defined by the sidewalls 206. Excited gas species flowthrough the plurality of through holes 314 and 324 via an indirect path.The excited gas species flow through the plurality of through holes 230of the gas distribution device 200 and into the lower chamber as shownin FIG. 8 . Likewise, reactant gas species flow through the annularchannel 220, the connecting channels 224 and the plurality of throughholes 232 into the lower chamber as shown in FIG. 7 .

Referring now to FIG. 13 , the light blocking structure 240 includes(from top to bottom) a first blocking plate 360 without holes and theannular plate 250. One or more spacers 280 may be used to define anaxial gap between the first blocking plate 360 and the annular plate250. A radially outer surface of the annular plate 250 is adjacent to orabuts the sidewall 206. Excited gas species flow around a radially outeredge of the first blocking plate 360 through the gap 308 and aredirected by the annular plate 250 inwardly. The excited gas species flowthrough the plurality of through holes 230 of the gas distributiondevice 200 and into the lower chamber as shown in FIG. 8 . Likewise,reactant gas species flow through the annular channel 220, theconnecting channels 224 and the plurality of through holes 232 into thelower chamber as shown in FIG. 7 .

In some examples, the axial spacing is in range from 0.5″ to 2″. In someexamples, the diameter of the top plate is in a range from 4″ to 11.5″.in some examples, the ring 208 adjusts with a plate diameter of thefirst blocking plate 360 to maintain no line of sight for the light fromplasma above the first blocking plate 360.

Referring now to FIG. 14 , another example of a gas distribution device200 includes a first showerhead 400 that includes a plurality of throughholes 410 and is arranged on the annular plate 250 above the dual gasplenum 202. In some examples, the hole size of the first showerhead 400is in a range from 0.1″ to 0.5″, spacing is in a range from 0.07″-2″,and a number of holes in the first showerhead 400 is in a range from 200to 400 holes.

A radially outer surface of the annular plate 250 is adjacent to orabuts the sidewall 206. Excited gas species flow through the firstshowerhead 400. The excited gas species then flow through the pluralityof through holes 230 of the gas distribution device 200 and into thelower chamber as shown in FIG. 8 . Likewise, reactant gas species flowthrough the annular channel 220, the connecting channels 224 and theplurality of through holes 232 into the lower chamber as shown in FIG. 7. Since the plurality of through holes 410 of the first showerhead 400are generally not aligned with the plurality of through holes 230 in thebottom surface 208, most of the VUV light generated by the plasma isblocked.

Referring now to FIGS. 15A and 15B, another gas distribution device 200is shown. Instead of using the plurality of through holes 230 having astraight path as shown in FIG. 8 , a plurality of through holes 420 areprovided that define an indirect path through the bottom surface 208 ofthe gas distribution device 200. For example, the plurality of throughholes 420 may have a first portion extending in first or axialdirection, a second portion connected to the first portion and extendingin a second direction (for example parallel to the substrate), and athird portion connected to the second portion and extending in the firstor axial direction. The plurality of through holes 420 may have otherpaths such as a diagonal path or a combination of diagonal, axial and/orradial. In some examples, the bottom surface 208 is made of multipleplates that are welded, bonded, fastened or otherwise attached together.For example in FIG. 15A, the bottom surface 208 includes first, secondand third plates 430, 432 and 434. The first plate 430 defines the firstportions, the second plate 432 defines the second portions and the thirdplate 434 defines the third portions. In FIG. 15B, the reactant gasflows in a manner that is similar to that shown in FIG. 7 .

Referring now to FIG. 16 , a gas distribution device 500 is shown. Thegas distribution device 500 delivers one or more reactant gas mixturesusing a center zone 502 and an edge zone 504. The center zone 502 islocated at a radially inner portion of the bottom surface 208 and theedge zone 504 is located around the center zone 502. The edge zone 504includes one or more inlets 510 that supply a first reactant gas mixtureto an annular channel 520 located around a radially outer edge of thebottom surface 208 and connecting channels 524. The connecting channels524 extend inwardly from the annular channel 520. Through holes (asshown above) extend downwardly from the annular channel 520 and/or theconnecting channels 524 into the lower chamber.

The central zone 502 includes one or more gas inlets 536 that supply asecond reactant gas mixture. The central zone 502 includes radialchannels 538 connected to an annular channel 540. The annular channel540 is connected to connecting channels 542. Through holes (as shownabove) extend downwardly from the annular channel 540 and/or theconnecting channels 542. A plurality of through holes 558 are arrangedin areas 550 located between the channels. The first and second gasmixtures may include the same or different gas species or ratios ofgases.

Referring now to FIGS. 17 and 18 , graphs illustrating net loss ofamorphous silicon (a-Si) for different process temperatures and periodsis shown. As can be appreciated, the a-Si experiences less than 2Angstroms of loss during processing, which is a reduction of 50% ascompared to prior processes.

Referring now to FIG. 19 , another example of a gas distribution device600 including a zoned dual gas plenum 602 is shown. The gas distributiondevice 600 includes a flange 604 that extends radially outwardly fromside wall 606 and a bottom surface 610 partially defining the dual gasplenum 602. The bottom surface 610 includes a first plurality of throughholes 620 (partially shown for clarity) extending from the upper chamberthrough the bottom surface 610 to the lower chamber. During use, excitedgas species generated by the plasma in the upper chamber flows throughthe first plurality of through holes 620 into the lower chamber. In someexamples, the first plurality of through holes 620 is arranged in aplurality of concentric circular rings (having different diameters) eachincluding a single row of uniformly spaced through holes.

The bottom surface 610 further includes a second plurality of throughholes 630 (partially shown for clarity) that are associated with a firstzone that is located radially outside of a circle 622. The bottomsurface 610 further includes a third plurality of through holes 640(partially shown for clarity) that are associated with a second zonelocated radially inside of the circle 622. In some examples, the secondand third plurality of through holes 630, 640 are arranged in aplurality of concentric circular rings (having different diameters) eachincluding a single row of uniformly spaced through holes. In someexamples, the concentric circular rings of the second and thirdplurality of through holes 630 and 640 are located between theconcentric circular rings of the first plurality of through holes 620 asshown.

One or more gas inlets 650-1, 650-2, etc. (collectively gas inlets 650)may be arranged along a radially outer surface of the flange 604. One ormore channels 652 in the flange 604, one or more channels 654 in theside wall 606, and one or more channels 656 in the bottom surface 610provide a fluid connection from the gas inlet 650-1 to the thirdplurality of through holes 640. In some examples, the one or morechannels 656 are arranged in a radial direction in the bottom surface610, although non-radial channels can be used. One or more channels 662in the flange 604, one or more channels 664 in the side wall 606, andone or more channels 666 in the bottom surface provide a fluidconnection from another gas inlet 650-2 to the second plurality ofthrough holes 630.

Referring now to FIG. 20 , a blocking plate 700 may be arranged in theupper chamber above the bottom surface 610 to block direct line of sightfrom the plasma to the substrate. The blocking plate 700 includes aplurality of concentric rings 710. Each of the concentric rings 710includes one or more arcuate slots 712. For example, each of theconcentric rings 710 includes arcuate slots 712 that are angularlyoffset from one another. In the example in FIG. 20 , each of theconcentric rings 710 includes three or four arcuate slots 712 that arespaced from one another, although additional or fewer arcuate slots 712can be used. In some examples, the arcuate slots 712 are not alignedwith the through holes 620 when the blocking plate 700 is arrangedrelative to the bottom surface 610. Adjacent plate portions 718 locatedbetween the arcuate slots 712 are aligned with the through holes 620 toblock the line of sight from the plasma to the substrate.

Referring now to FIG. 21 , a partial cross-section of the bottom surface610 of the dual gas plenum 602 is shown. The blocking plate 700 islocated on the bottom surface 610 or is spaced therefrom by one or morespacers 722 as described above. The bottom surface 610 includes annularchannels 730, 740 that are in fluid communication with the channel 656or 666 depending upon the radial position of the annular channel 730,740. In some examples, the annular channels 730, 740 are concentric andare located between the concentric rings of defined by the firstplurality of through holes 620. The annular channels 730 are in fluidcommunication with the second plurality of through holes 630. Theannular channels 740 are in fluid communication with the third pluralityof through holes 640.

In use, excited gas species are supplied by the plasma in the upperchamber through the first plurality of through holes 620 to the lowerchamber. The blocking plate 700 blocks a line of sight from the plasmato the substrate. A first reactant gas mixture is supplied to the gasinlet 650-1. The first reactant gas mixture flows through the channels652, 654 and 656 into the annular channel 730 and through the secondplurality of through holes 630 into a radially outer portion of thelower chamber. A second reactant gas mixture is supplied to the gasinlet 650-2. The second reactant gas mixture flows through the channels662, 664 and 666 into the annular channel 740 and through the thirdplurality of through holes 640 into a radially inner portion of thelower chamber. In some examples, the first and second reactant gasmixtures are the same reactant gas mixture, although different reactantgas mixtures can be used. In some examples, the first and secondreactant gas mixtures are delivered at different flow rates, althoughthe same flow rate can be used.

In some examples, the inner zone (inside of the circle 622) is definedby a center of the bottom surface to a radial distance equal to 40% to70% of the maximum radial distance. The outer zone (outside of thecircle 622) is defined radially outside of the inner zone. In someexamples, the inner zone (inside of the circle 622) is defined by acenter of the bottom surface and a radial distance in a range from 70 to120 mm. The outer zone (outside of the circle 622) is defined an outeredge of the inner zone to 150 mm. In some examples, the first pluralityof through holes 620 includes 200 to 4000 holes. In some examples, theblocking plate 700 is spaced in a range from 0.07″ to 3″ from the bottomsurface 610.

Referring now to FIG. 22 , a substrate processing system 750 thatperforms plasma pulsing to enhance an ash rate during photoresiststripping and/or a removal rate during film removal is shown. In someexamples, optical feedback is used to identify predetermined RF pulsingparameters and/or to control the plasma pulsing. For example, an opticalemission spectroscopy (OES) sensor 760 generates optical feedback bydetecting spectra of the plasma. In some examples, the OES sensor 760 isarranged in a viewport (not shown) arranged in a sidewall of theprocessing chamber 60. Intensities of one or more specific emissionlines corresponding to the selected metastable species are monitored. Insome examples, a collimating tube (not shown) is used between theviewport and the OES sensor 760. An output of the OES sensor 760 is fedback to the system controller 140.

An RF generating system 770 further includes a pulse modulator 772 thatreceives an output of the RF generator 88 and performs plasma pulsing bymodulating the power output of the RF generator 88 using a modulatingwaveform such as a square, rectangular, triangular, saw tooth,sinusoidal or other type of modulating waveform. RF pulsing parameterssuch as the frequency and/or duty cycle of the modulating waveform canalso be varied. The system controller 140 adjusts one or more of the RFpulsing parameters based on the feedback. In some examples, the RFpulsing parameters are varied to identify a set of RF pulsing parameterswhere the intensity of the metastable species during a first state (suchas an ON state) is less than the intensity of the metastable speciesduring a second state (such as an OFF state).

Referring now to FIGS. 23A and 23B, metastable species are enhanced whenthe RF plasma is pulsed as compared to non-pulsed plasma for at leasttwo reasons. In FIG. 23A, enhanced long lifetime species are createdwhen the plasma is pulsed. In this example, the plasma is pulsed using asquare wave signal.

The metastable species have a longer lifetime than ions and electrons.For example, He metastable species are at least 3 orders of magnitudehigher than He+ and excited states. As can be appreciated, high energyAr species can also be generated by pulsed plasma. Use of pulsed Arplasma will generally cost less than use of He plasma. When pulsedplasma is used, more metastable species will diffuse into the substrateand the ash rate is enhanced. In some examples, a 25% improvement in ashrate can be achieved as compared to non-pulsed plasma.

Fast electrons during the second state (such as the plasma source offstate) increase specific line optical emission (for example, 420 nm and549.6 nm emission lines for Ar plasma). Systems and methods describedherein monitor intensity levels at specific line optical emissionwavelengths of the metastable species and control the RF pulsingparameters based thereon to ensure that the intensity of metastablespecies during the first state is less than the intensity of themetastable species during the second state.

In FIG. 23B, a fast electron effect is also created by pulsing theplasma. As can be seen, emission intensity of the metastable speciesincreases when the RF plasma is off after a period when the RF plasma ison. When the modulating waveform is on, production of metastable speciesoccurs due to electron collision. When the modulating waveform is off,reproduction occurs by recombination. Fast electrons are created whenthe modulating waveform is off by chem-ionization of slow electrons andmetastable species, which further increases metastable species density.

While a fixed duty cycle can be used, the duty cycle can also be variedbased on feedback from the OES sensor. In other words, the intensity atone or more wavelengths is monitored. When the intensity during an OFFperiod falls below the intensity during a prior ON period of themodulating waveform, the modulating waveform can be turned back ON for apredetermined period and then the modulating waveform is turned back OFFto create enhanced metastable species intensity.

Referring now to FIGS. 24A to 24C, examples of pulsed signals that areused to modulate the RF plasma signal are shown. In FIG. 24A, amodulating waveform includes a pulsed square wave that has a period oft, an on time of t_(ON) and an off time of t_(OFF). The duty cycle isdefined as t_(ON)/t. The amplitude, frequency, and/or duty cycle isvaried and optical feedback is used to identify pairs of RF pulsingparameters where the intensity of metastable species during the firststate is less than the intensity of metastable species during the secondstate. In FIG. 24B, both the modulating waveform and the RF plasmasignal are shown. In FIG. 24C, a pulsed dual level1-to-level2 signalmodulates the RF plasma signal.

Referring now to FIGS. 25A to 25D, other examples of pulsed signals formodulating the RF plasma signal in addition to those shown and describedabove are shown. In FIG. 25A, a triangular-shaped waveform may be usedto modulate the RF plasma signal. In FIG. 25B, a sinusoidal-shapedwaveform may be used to modulate the RF plasma signal. In FIG. 25C, anincreasing saw tooth waveform may be used to modulate the RF plasmasignal. In FIG. 25D, a decreasing saw tooth waveform may be used tomodulate the RF plasma signal.

Referring now to FIG. 26 , a method 800 for identifying pairs of RFparameters of the modulating signal that can be used to provide adesired intensity ratio (the intensity during a first state divided bythe intensity during the second state). The method 800 uses opticalfeedback from an optical emission spectroscopy (OES) sensor to monitorone or more wavelengths corresponding to the selected metastablespecies. The feedback is further used to identify pairs of RF pulsingparameters of the modulating signal having the desired intensity ratio.In some examples, the desired intensity ratio is less than 1. In otherexamples, the intensity ratio is minimized.

During each iteration, the method selects an RF pulsing parameter(corresponding to a first state of the modulating signal) and measuresthe intensity using the OES sensor. The RF pulsing parameter is varied(to a second state of the modulating signal) and then the methodmeasures the intensity using the OES sensor. Examples of RF pulsingparameters of the modulating signal that can be switched include a dutycycle of the modulating signal (e.g. between two values such as 0% and100%, 10% and 100%, zero and a non-zero percentage value, or twonon-zero percentage values), a pulsing frequency of the modulatingsignal (such as two different frequencies), magnitude(s) of themodulating signal, a shape of the modulating signal, and/or combinationsthereof.

Identification of potential RF pulsing parameters can be performed withor without a substrate located in the processing chamber. At 824, plasmais supplied from a plasma source via a pulse modulator. In someexamples, the pulse modulator begins operation in a first pulsing state.The pulse modulator can be used to vary the RF pulsing parametersbetween the first and second states.

At 836, the intensity at one or more predetermined wavelengthscorresponding to the selected metastable species is monitored using theOES sensor. At 840, the RF pulsing parameter that will be varied betweenstates is selected. For example, duty cycle may be varied from 0% or 20%to 100% to identify duty cycles having an intensity ratio that is lessthan 1. At 842, the RF pulsing parameters are varied between the firstand second states during first and second consecutive periods that maybe repeated one or more times. At 844, the intensity is measured at oneor more wavelengths (corresponding to the metastable species) during thefirst and second states. If the intensity ratio is less than 1 asdetermined at 846, then the RF pulsing parameters can be used and theplasma source can be extinguished at 848. If 846 is false, the processcan be repeated by returning to 840 and selecting other RF pulsingparameters to vary.

Referring now to FIG. 27 , a method 850 switches the RF parametersbetween the first and second states during processing of the substrateto enhance the ashing performed by the metastable species. In someexamples, the RF pulsing parameters for the first and second states thatare identified in the method of FIG. 26 can be used. Timing of theswitching between the first and second states can be controlled usingfeedback from the OES sensor.

At 852, a substrate is arranged in the processing chamber. At 854,plasma is supplied from a plasma source and a pulse modulator operatesin a first pulsing state. At 856, ions and UV photons are filtered usinga showerhead. At 858, a secondary gas is supplied between the showerheadand a substrate support.

At 860, the intensity of the OES sensor is monitored at predeterminedwavelengths corresponding to the metastable species. At 864, theintensity during the first state is compared to the intensity in thesecond state. The intensity in the second state can correspond to astored value from a prior period, a predetermined value, or a functionof one or more intensity values from a prior period. If the firstintensity is less than the second intensity as determined at 868, themethod switches states at 870. If the first intensity is greater thanthe second intensity, the method continues at 874 and determines whetherthe strip period is over. If 874 is false, then the method continues at860. If 874 is true, the plasma source and the secondary gas are turnedoff at 878.

Referring now to FIG. 28 , a method 900 switches the RF parametersbetween the first and second states during processing of the substrate.The RF pulsing parameters for the first and second states that areidentified in the method of FIG. 26 can be used. Rather than usingfeedback, switching between the first and second states is performed atpredetermined intervals.

At 910, the method determines whether the pulsing state is equal to thefirst pulsing state. If 910 is true, the method determines whether thefirst pulse period corresponding to the first pulsing state is up at912. If 912 is false, the method continues at 920. If 912 is true, themethod continues at 914 and switches to the second pulsing state. Themethod continues from 914 to 920.

When 910 is false, the method continues at 924 and determines whetherthe pulsing state is equal to the second pulsing state. When 924 istrue, the method continues at 928 and determines whether the secondpulse period is up. When 928 is false, the method continues at 920. When928 is true, the method continues at 934 and switches from the secondpulsing state to the first pulsing state. The method continues from 934to 920.

At 920, the method determines whether the stripping period is over. If920 is false, the method continues at 910. When 920 is true, the methodcontinues at 940 and turns off the plasma source and secondary gas.

The foregoing description is merely illustrative in nature and is in noway intended to limit the disclosure, its application, or uses. Thebroad teachings of the disclosure can be implemented in a variety offorms. Therefore, while this disclosure includes particular examples,the true scope of the disclosure should not be so limited since othermodifications will become apparent upon a study of the drawings, thespecification, and the following claims. It should be understood thatone or more steps within a method may be executed in different order (orconcurrently) without altering the principles of the present disclosure.Further, although each of the embodiments is described above as havingcertain features, any one or more of those features described withrespect to any embodiment of the disclosure can be implemented in and/orcombined with features of any of the other embodiments, even if thatcombination is not explicitly described. In other words, the describedembodiments are not mutually exclusive, and permutations of one or moreembodiments with one another remain within the scope of this disclosure.

Spatial and functional relationships between elements (for example,between modules, circuit elements, semiconductor layers, etc.) aredescribed using various terms, including “connected,” “engaged,”“coupled,” “adjacent,” “next to,” “on top of,” “above,” “below,” and“disposed.” Unless explicitly described as being “direct,” when arelationship between first and second elements is described in the abovedisclosure, that relationship can be a direct relationship where noother intervening elements are present between the first and secondelements, but can also be an indirect relationship where one or moreintervening elements are present (either spatially or functionally)between the first and second elements. As used herein, the phrase atleast one of A, B, and C should be construed to mean a logical (A OR BOR C), using a non-exclusive logical OR, and should not be construed tomean “at least one of A, at least one of B, and at least one of C.”

In some implementations, a controller is part of a system, which may bepart of the above-described examples. Such systems can comprisesemiconductor processing equipment, including a processing tool ortools, chamber or chambers, a platform or platforms for processing,and/or specific processing components (a wafer pedestal, a gas flowsystem, etc.). These systems may be integrated with electronics forcontrolling their operation before, during, and after processing of asemiconductor wafer or substrate. The electronics may be referred to asthe “controller,” which may control various components or subparts ofthe system or systems. The controller, depending on the processingrequirements and/or the type of system, may be programmed to control anyof the processes disclosed herein, including the delivery of processinggases, temperature settings (e.g., heating and/or cooling), pressuresettings, vacuum settings, power settings, radio frequency (RF)generator settings, RF matching circuit settings, frequency settings,flow rate settings, fluid delivery settings, positional and operationsettings, wafer transfers into and out of a tool and other transfertools and/or load locks connected to or interfaced with a specificsystem.

Broadly speaking, the controller may be defined as electronics havingvarious integrated circuits, logic, memory, and/or software that receiveinstructions, issue instructions, control operation, enable cleaningoperations, enable endpoint measurements, and the like. The integratedcircuits may include chips in the form of firmware that store programinstructions, digital signal processors (DSPs), chips defined asapplication specific integrated circuits (ASICs), and/or one or moremicroprocessors, or microcontrollers that execute program instructions(e.g., software). Program instructions may be instructions communicatedto the controller in the form of various individual settings (or programfiles), defining operational parameters for carrying out a particularprocess on or for a semiconductor wafer or to a system. The operationalparameters may, in some embodiments, be part of a recipe defined byprocess engineers to accomplish one or more processing steps during thefabrication of one or more layers, materials, metals, oxides, silicon,silicon dioxide, surfaces, circuits, and/or dies of a wafer.

The controller, in some implementations, may be a part of or coupled toa computer that is integrated with the system, coupled to the system,otherwise networked to the system, or a combination thereof. Forexample, the controller may be in the “cloud” or all or a part of a fabhost computer system, which can allow for remote access of the waferprocessing. The computer may enable remote access to the system tomonitor current progress of fabrication operations, examine a history ofpast fabrication operations, examine trends or performance metrics froma plurality of fabrication operations, to change parameters of currentprocessing, to set processing steps to follow a current processing, orto start a new process. In some examples, a remote computer (e.g. aserver) can provide process recipes to a system over a network, whichmay include a local network or the Internet. The remote computer mayinclude a user interface that enables entry or programming of parametersand/or settings, which are then communicated to the system from theremote computer. In some examples, the controller receives instructionsin the form of data, which specify parameters for each of the processingsteps to be performed during one or more operations. It should beunderstood that the parameters may be specific to the type of process tobe performed and the type of tool that the controller is configured tointerface with or control. Thus as described above, the controller maybe distributed, such as by comprising one or more discrete controllersthat are networked together and working towards a common purpose, suchas the processes and controls described herein. An example of adistributed controller for such purposes would be one or more integratedcircuits on a chamber in communication with one or more integratedcircuits located remotely (such as at the platform level or as part of aremote computer) that combine to control a process on the chamber.

Without limitation, example systems may include a plasma etch chamber ormodule, a deposition chamber or module, a spin-rinse chamber or module,a metal plating chamber or module, a clean chamber or module, a beveledge etch chamber or module, a physical vapor deposition (PVD) chamberor module, a chemical vapor deposition (CVD) chamber or module, anatomic layer deposition (ALD) chamber or module, an atomic layer etch(ALE) chamber or module, an ion implantation chamber or module, a trackchamber or module, and any other semiconductor processing systems thatmay be associated or used in the fabrication and/or manufacturing ofsemiconductor wafers.

As noted above, depending on the process step or steps to be performedby the tool, the controller might communicate with one or more of othertool circuits or modules, other tool components, cluster tools, othertool interfaces, adjacent tools, neighboring tools, tools locatedthroughout a factory, a main computer, another controller, or tools usedin material transport that bring containers of wafers to and from toollocations and/or load ports in a semiconductor manufacturing factory.

What is claimed is:
 1. A substrate processing system for selectivelyetching a substrate, comprising: a processing chamber including an upperportion in which a plasma is generated and a lower portion in which noplasma is generated; a first gas delivery system to supply an inert gasspecies to the upper portion of the processing chamber; a plasmagenerating system to generate the plasma in the upper portion of theprocessing chamber, the plasma including ions and metastable species; asecond gas delivery system to supply a reactive gas species; a gasdistribution device arranged between the upper and lower portions of theprocessing chamber to receive the reactive gas species, to remove ionsfrom the plasma, to block ultraviolet (UV) light generated by the plasmaand to deliver the metastable species to the lower portion of theprocessing chamber, wherein the gas distribution device comprises: atleast one sidewall; a flange extending radially outwardly from the atleast one sidewall; a dual gas plenum comprising: an upper surface and alower surface forming an upper surface and a lower surface of the dualgas plenum; a gas inlet to receive the reactive gas species from thesecond gas delivery system; an annular channel formed between the uppersurface and the lower surface of the dual gas plenum and connected tothe gas inlet; a plurality of connecting channels extending between andconnected to opposite sides of the annular channel; a first plurality ofthrough holes extending from the connecting channels downwardly throughthe lower surface of the dual gas plenum to deliver the reactive gasspecies to the lower portion of the processing chamber; a secondplurality of through holes in the lower surface of the dual gas plenumextending from the upper surface to the lower surface of the dual gasplenum to deliver the metastable species to the lower portion of theprocessing chamber; and a light blocking structure comprising at leastone plate having a third plurality of through holes and supported by theat least one side wall, wherein the light blocking structure prevents aline of sight path between the plasma in the upper portion of theprocessing chamber and the substrate in the lower portion of theprocessing chamber; and a substrate support arranged below the gasdistribution device in the lower portion of the processing chamber tosupport the substrate, wherein the metastable species transfer energy tothe reactive gas species to selectively etch one exposed material of thesubstrate more than at least one other exposed material of thesubstrate.
 2. The substrate processing system of claim 1, wherein theone exposed material of the substrate includes photoresist.
 3. Thesubstrate processing system of claim 2, wherein the substrate processingsystem etches the photoresist at a ratio greater than 50:1 relative toat least one other exposed material of the substrate.
 4. The substrateprocessing system of claim 3, wherein the at least one other exposedmaterial is selected from a group consisting of silicon, silicongermanium, and silicon dioxide.
 5. The substrate processing system ofclaim 1, wherein the inert gas species is selected from a first groupconsisting of helium, argon, neon, krypton and xenon; and wherein thereactive gas species is selected from a second group consisting ofmolecular oxygen, molecular nitrogen, molecular hydrogen, nitrogentrifluoride and carbon tetrafluoride.
 6. The substrate processing systemof claim 1, wherein the plasma generating system includes an inductivecoil arranged around an outer surface of the upper portion of theprocessing chamber and wherein the plasma generating system selectivelysupplies 500 W to 5 kW to the inductive coil to generate the plasma. 7.The substrate processing system of claim 1, wherein the substratesupport controls a temperature of the substrate to a predeterminedtemperature range from 75° C. to 225° C. during etching.
 8. Thesubstrate processing system of claim 1, wherein the inert gas speciesand the reactive gas species are supplied at a flow rate of 50 sccm to10 slm.
 9. The substrate processing system of claim 1, wherein in thelight blocking structure, the at least one plate having the thirdplurality of through holes comprises: a first light blocking plateincluding a first set of through holes of the third plurality of throughholes; and a second light blocking plate that is located between andspaced from the first light blocking plate and the gas distributiondevice and that includes a second set of through holes of the thirdplurality of through holes, wherein the first set of through holes ofthe third plurality of through holes is not aligned with the second setof through holes of the third plurality of through holes, and whereinthe metastable species flow through the first set of through holes ofthe third plurality of through holes and the second plurality of throughholes of the third plurality of through holes to the dual gas plenum.10. The substrate processing system of claim 9, wherein the first set ofthrough holes of the third plurality of through holes and the second setof through holes of the third plurality of through holes have a diameterin a range from 0.1″ to 2″.
 11. The substrate processing system of claim9, wherein the first light blocking plate and the second light blockingplate have a thickness in a range from 0.1″ to 0.5″.
 12. The substrateprocessing system of claim 9, wherein each of the first set of throughholes of the third plurality of through holes and the second set ofthrough holes of the third plurality of through holes comprises 10 to3000 holes.
 13. The substrate processing system of claim 9, furthercomprising an annular plate that is located above the first lightblocking plate, that includes a radially outer edge that extends to asidewall of the upper portion of the processing chamber and thatincludes a radially inner edge having a diameter that is less than anouter diameter of the first light blocking plate.
 14. The substrateprocessing system of claim 1, wherein in the light blocking structure,the at least one plate having the third plurality of through holescomprises: a first light blocking plate without through holes andincluding a radially outer edge that is spaced from a sidewall of theupper portion of the processing chamber; and a second light blockingplate that is located between and spaced from the first light blockingplate and the dual gas plenum and that includes the third plurality ofthrough holes, wherein the metastable species flow around the firstlight blocking plate and through the plurality of through holes of thesecond light blocking plate to the dual gas plenum.
 15. The substrateprocessing system of claim 1, wherein: the second plurality of throughholes define an indirect path through the gas distribution device fromthe upper surface to the lower surface of the gas distribution device.16. The substrate processing system of claim 1, wherein the plasmagenerating system further comprises a pulse modulator configured to varya pulsing parameter of an RF signal that generates the plasma duringetching.
 17. The substrate processing system of claim 16, wherein thepulse modulator varies at least one of a duty cycle and an amplitude ofthe RF signal supplied during etching.
 18. The substrate processingsystem of claim 16, wherein the pulse modulator varies the pulsingparameter between a first state having a first RF power and second statehaving a second RF power that is less than the first RF power.
 19. Thesubstrate processing system of claim 18, wherein the pulse modulatorswitches between the first state and the second state at predeterminedintervals during etching.
 20. The substrate processing system of claim18, wherein the pulse modulator receives an optical feedback signal andswitches between the first state and the second state during etchingbased on the optical feedback signal.
 21. The substrate processingsystem of claim 18, wherein a first intensity of the metastable speciesduring the first state is less than a second intensity of the metastablespecies during the second state.
 22. The substrate processing system ofclaim 18 wherein the RF signal has an envelope selected from a groupconsisting of a square wave, a rectangular wave, a sinusoidal wave, anda saw tooth wave.
 23. The substrate processing system of claim 18wherein the RF signal has a rectangular wave envelope and switches at aduty cycle that is less than 100% between a first amplitude and a secondamplitude.
 24. The substrate processing system of claim 23, wherein thefirst amplitude is greater than the second amplitude and wherein thesecond amplitude is greater than or equal to zero.
 25. The substrateprocessing system of claim 1, wherein the gas distribution device andthe substrate support are unconnected to a power source.
 26. Thesubstrate processing system for selectively etching a substrate,comprising: a processing chamber including an upper portion in which aplasma is generated and a lower portion in which no plasma is generated;a first gas delivery system to supply an inert gas species to the upperportion of the processing chamber; a plasma generating system togenerate the plasma in the upper portion of the processing chamber, theplasma including ions and metastable species; a second gas deliverysystem to supply a reactive gas species; a gas distribution devicearranged between the upper and lower portions of the processing chamberto receive the reactive gas species, to remove ions from the plasma, toblock ultraviolet (UV) light generated by the plasma and to deliver themetastable species to the lower portion of the processing chamber,wherein the gas distribution device comprises: at least one sidewall; aflange extending radially outwardly from the at least one sidewall; adual gas plenum comprising: an upper surface and a lower surface formingan upper surface and a lower surface of the dual gas plenum; a gas inletto receive the reactive gas species from the second gas delivery system;an annular channel formed between the upper surface and the lowersurface of the dual gas plenum and connected to the gas inlet; aplurality of connecting channels extending between and connected toopposite sides of the annular channel; a first plurality of throughholes extending from the connecting channels downwardly through thelower surface of the dual gas plenum to deliver the reactive gas speciesto the lower portion of the processing chamber; a second plurality ofthrough holes in the lower surface of the dual gas plenum extending fromthe upper surface to the lower surface of the dual gas plenum to deliverthe metastable species to the lower portion of the processing chamber;and a light blocking structure comprising at least one plate andsupported by the at least one side wall, wherein the light blockingstructure prevents a line of sight path between the plasma in the upperportion of the processing chamber and the substrate in the lower portionof the processing chamber, wherein the at least one plate comprises: alight blocking plate without through holes and including a radiallyouter edge that is spaced from a sidewall of the upper portion of theprocessing chamber; and an annular plate that is spaced from the lightblocking plate and the gas distribution device, that extends to thesidewall of the upper portion of the processing chamber and that has aninner diameter that is less than an outer diameter of the light blockingplate, wherein the metastable species flow around the light blockingplate and through the inner diameter of the annular plate to the dualgas plenum; and a substrate support arranged below the gas distributiondevice in the lower portion of the processing chamber to support thesubstrate, wherein the metastable species transfer energy to thereactive gas species to selectively etch one exposed material of thesubstrate more than at least one other exposed material of thesubstrate.
 27. A substrate processing system for selectively etching asubstrate, comprising: a processing chamber including an upper portionin which a plasma is generated and a lower portion in which no plasma isgenerated; a first gas delivery system to supply an inert gas species tothe upper portion of the processing chamber; a plasma generating systemto generate the plasma in the upper portion of the processing chamber,the plasma including ions and metastable species; a second gas deliverysystem to supply first and second reactive gas species; a gasdistribution device arranged between the upper and lower portions of theprocessing chamber to receive the first and second reactive gas species,to remove ions from the plasma, to block ultraviolet (UV) lightgenerated by the plasma and to deliver the metastable species to thelower portion of the processing chamber, wherein the gas distributiondevice comprises: at least one sidewall; a flange extending radiallyoutwardly from the at least one sidewall; a dual gas plenum comprising:an upper surface and a lower surface forming an upper surface and alower surface of the dual gas plenum; a first gas inlet to receive thefirst reactive gas species from the second gas delivery system; a secondgas inlet to receive the second reactive gas species from the second gasdelivery system; a first annular channel formed adjacent to a radiallyouter edge of the gas distribution device and connected to the first gasinlet; a second annular channel formed radially inwardly from the firstannular channel and connected to the second gas inlet; first channelsconnected to the first annular channel to deliver the first reactive gasspecies from the first gas inlet to a first plurality of locations in afirst zone above the substrate, wherein a first set of the firstchannels extend between and are connected to opposite sides of the firstannular channel, and wherein a second set of the first channels extendradially inwardly up to the second annular channel; second channelsextending between and connected to opposite sides of the second annularchannel to deliver the second reactive gas species from the second gasinlet to a second plurality of locations in a second zone above thesubstrate; a first plurality of through holes extending from the firstchannels downwardly through the lower surface of the dual gas plenum todeliver the first reactive gas species to the lower portion of theprocessing chamber; a second plurality of through holes extending fromthe second channels downwardly through the lower surface of the dual gasplenum to deliver the second reactive gas species to the lower portionof the processing chamber; and a third plurality of through holesextending from the upper surface to the lower surface of the dual gasplenum to deliver the metastable species to the lower portion of theprocessing chamber; and a light blocking structure comprising a platehaving a fourth plurality of through holes and supported by the at leastone side wall, wherein the light blocking structure prevents a line ofsight path between the plasma in the upper portion of the processingchamber and the substrate in the lower portion of the processingchamber; and a substrate support arranged below the gas distributiondevice in the lower portion of the processing chamber to support thesubstrate, wherein the metastable species transfer energy to the firstand second reactive gas species to selectively etch one exposed materialof the substrate more than at least one other exposed material of thesubstrate.
 28. The substrate processing system of claim 27, wherein:portions of the first channels extends radially inwardly to the firstzone; portions of the second channels extends radially inwardly to thesecond zone; and the first plurality of through holes, the secondplurality of through holes, and the third plurality of through holes arearranged in concentric circles.
 29. The substrate processing system ofclaim 27, wherein in the light blocking structure, the plate having thefourth plurality of through holes comprises concentric rings, eachconcentric ring including a plurality of arcuate holes that areangularly offset from each other and that are misaligned relative to thefirst plurality of through holes, the second plurality of through holes,and the third plurality of through holes; and wherein portions of theplate between the arcuate holes are aligned with the first plurality ofthrough holes to block the line of sight path from the plasma to thesubstrate.
 30. The substrate processing system of claim 27, wherein: thefirst and second annular channels are concentric and coplanar, and thesecond annular channel has a smaller diameter than the first annularchannel.
 31. The substrate processing system of claim 27, wherein thefirst channels and the second channels extend interstitially.
 32. Asubstrate processing system for selectively etching a substrate,comprising: a processing chamber including an upper portion in which aplasma is generated and a lower portion in which no plasma is generated;a first gas delivery system to supply an inert gas species to the upperportion of the processing chamber; a plasma generating system togenerate the plasma in the upper portion of the processing chamber, theplasma including ions and metastable species; a second gas deliverysystem to supply first and second reactive gas species; a gasdistribution device arranged between the upper and lower portions of theprocessing chamber to receive the first and second reactive gas species,to remove ions from the plasma, to block ultraviolet (UV) lightgenerated by the plasma and to deliver the metastable species to thelower portion of the processing chamber, wherein the gas distributiondevice comprises: at least one sidewall; a flange extending radiallyoutwardly from a sidewall of the gas distribution device; a dual gasplenum comprising: an upper surface and a lower surface forming an uppersurface and lower surface of the dual gas plenum; first and second gasinlets arranged along a radially outer surface of the flange to receivethe first and second reactive gas species from the second gas deliverysystem, respectively; first, second, and third channels formedrespectively in the flange, the sidewall, and the lower surface of thegas distribution device, the first channel connected to the first gasinlet and to the second and third channels; fourth, fifth, and sixthchannels formed respectively in the flange, the sidewall, and the lowersurface of the gas distribution device, the fourth channel connected tothe second gas inlet and to the fifth and sixth channels; and a firstplurality of through holes extending from the upper surface to the lowersurface to deliver the metastable species to the lower portion of theprocessing chamber; a second plurality of through holes extending fromthe third channels downwardly through the lower surface to deliver thefirst reactive gas species to the lower portion of the processingchamber; and a third plurality of through holes extending from the sixthchannels downwardly through the lower surface to deliver the secondreactive gas species to the lower portion of the processing chamber; anda light blocking structure comprising a plate having a fourth pluralityof through holes and supported by the at least one side wall, whereinthe light blocking structure prevents a line of sight path between theplasma in the upper portion of the processing chamber and the substratein the lower portion of the processing chamber; and a substrate supportarranged below the gas distribution device in the lower portion of theprocessing chamber to support the substrate, wherein the metastablespecies transfer energy to the first and second reactive gas species toselectively etch one exposed material of the substrate more than atleast one other exposed material of the substrate.
 33. The substrateprocessing system of claim 32, wherein the gas distribution devicefurther comprises: the sixth channels extend radially inwardly from thefifth channels up to a center of the lower surface; the third channelsextend radially inwardly from the sixth channels and are shorter thanthe sixth channels; a first plurality of annular channels arranged inthe lower surface and connected to the third channels; and a secondplurality of annular channels arranged in the lower surface andconnected to the sixth channels; wherein the first plurality of throughholes are arranged in concentric circles; and wherein the first andsecond plurality of annular channels are concentric and coplanar and arearranged between the concentric circles.
 34. The substrate processingsystem of claim 32, wherein: the first plurality of through holes arearranged in first concentric circles; and the second and third pluralityof through holes are arranged in second concentric circles that arearranged between the first concentric circles.
 35. The substrateprocessing system of claim 32, wherein in the light blocking structure,the plate having the fourth plurality of through holes comprisesconcentric rings, each concentric ring including a plurality of arcuateholes that are angularly offset from each other and that are misalignedrelative to the first plurality of through holes, the second pluralityof through holes, and the third plurality of through holes; and whereinportions of the plate between the arcuate holes are aligned with thefirst plurality of through holes to block the line of sight path fromthe plasma to the substrate.